A group of prominent scientists is calling on California governor Jerry Brown to incorporate tropical forest conservation into the state’s cap-and-trade regulation.

California has been mulling the inclusion of tropical forests in its cap-and-trade regulation, which was authorized by the Global Warming Solutions Act of 2006 (AB32), for a decade.

If California were to adopt the tropical forest standard in its climate law, the move would signal to tropical forests nations that industrialized countries are willing to put money into forest conservation efforts as part of their climate change mitigation frameworks, say the scientists.

A group of prominent scientists is calling on California governor Jerry Brown to incorporate tropical forest conservation into the state’s cap-and-trade regulation ahead of next month’s Global Climate Action Summit, which is being held in San Francisco.

The letter, signed by 20 scientists from a range of institutions, highlights the climate change mitigation potential of tropical forests, which lock up vast amounts of carbon in their vegetation and soils.

“The best science points to an important part of the climate change solution that you are uniquely positioned to unlock: tropical forests,” the scientists write. “These carbon- and species-rich ecosystems could deliver up to a fourth of the carbon emissions reductions needed by 2030 to avoid dangerous climate change. Slowing the deforestation and degradation of tropical forests, the source of as much as one fifth of global emissions, while allowing damaged forests to recover is one of the most cost-effective, near-term steps towards a zero net carbon budget globally.”

Deforestation and forest degradation is the largest source of greenhouse gas emissions from human activities after power generation.

California has been mulling the inclusion of tropical forests in its cap-and-trade regulation, which was authorized by the Global Warming Solutions Act of 2006 (AB32), for a decade. During that time, the state has been developing a tropical forest standard in consultation with experts and using feedback from a set of forest conservation pilot projects run under Governors’ Climate and Forests Task Force, an initiative involving leaders from states and provinces in Brazil, Colombia, Ecuador, Indonesia, Ivory Coast, Mexico, Nigeria, Peru, Spain, and the United States.

If California were to adopt the tropical forest standard in its climate law, the move would signal to tropical forests nations that industrialized countries are willing to put money into forest conservation efforts as part of their climate change mitigation frameworks, say the scientists.

“Moving forward to adopt this standard in a regulation would inspire and motivate tropical forest governments around the world to put the brakes on the loss and degradation of tropical forests while allowing damaged forests to recover,” states the letter. “It would establish the foundation for the first regulated market for carbon emissions reductions from tropical forests, providing an important precedent and example to other states, provinces, and nations that are poised to emulate it.”

“The high bar that the California Air Resources Board has set for the environmental and social safeguards of this market would inform the design of similar markets under consideration.”

Dan Nepstad, a tropical forest ecologist the Earth Innovation Institute who has been closely involved with the Governors’ Climate and Forests Task Force, told Mongabay that “All of the heavy lifting has been done” on the tropical forest standard, including a multi-year process to develop recommendations, establish safeguards, hold public hearings, and articulate how the international offset mechanism would work.

Nepstad added that action by California could usher in a wave of entities including forest conservation-based offsets in cap-and-trade programs.

“California has a set a high bar, and would link with jurisdictional REDD programs,” he told Mongabay. “International offsets are included in the cap-and-trade extension through 2030, although at a very low level, in terms of the percentage of emissions reductions. Nonetheless, the California standard would likely encourage other markets — International Civil Aviation Organization (ICAO), even China cap-and-trade, and others — to move forward.”